8085 Programs

Gursharan Singh Tatla Page 1 of 3

Program 16: Multiply two 8-bit numbers.

Flowchart:

Initialize register A with 0.

Stop

Add B with A.

Decrement register C.

Is

C = 0?

Increment H-L pair.

Start

Load H-L pair with address

of first operands memory location.

Move the first operand from

memory to register B.

Increment H-L pair to point

to next memory location.

Move the second operand

from memory to register C.

Move the result from

accumulator to memory.

Yes

No

8085 Programs

Gursharan Singh Tatla Page 2 of 3

Program:

Address Mnemonics Operand Opcode Remarks

2000 LXI H, 3000H 21 Load H-L pair with address 3000H.

2001 00 Lower-order of 3000H.

2002 30 Higher-order of 3000H.

2003 MOV B, M 46 Move the 1st operand from memory to reg. B.

2004 INX H 23 Increment H-L pair.

2005 MOV C, M 4E Move the 2nd

operand from memory to reg. C.

2006 MVI A, 00H 3E Initialize accumulator with 00H.

2007 00 Immediate value 00H.

2008 ADD B 80 Add B with A.

2009 DCR C 0D Decrement reg. C (counter).

200A JNZ 2008H C2 Jump back to address 2008H if C 0.

200B 08 Lower-order of 2008H.

200C 20 Higher-order of 2008H.

200D INX H 23 Increment H-L pair.

200E MOV M, A 77 Move the result from accumulator to memory.

200F HLT 76 Halt.

Explanation:

This program multiplies two operands stored in memory location 3000H and 3001H, using

successive addition method.

In successive addition method, the second operand is considered as counter, and the first

number is added with itself until counter decrements to zero.

Let us assume that the operands stored at memory location 3000H is 02H and 3001H is 05H.

Then, by using successive addition method, we get 02H + 02H + 02H + 02H + 02H = 0AH.

Initially, H-L pair is loaded with the address of first memory location.

The first operand is moved to register B from memory location 3000H and H-L pair is

incremented to point to next memory location.

The second operand is moved to register C from memory location 3001H to act as counter.

Accumulator is initialized to 00H.

Register B is added with accumulator and the result is stored in accumulator.

Register C (counter) is decremented by 1.

Then, counter is checked for zero. If it hasnt become zero yet, then register B is again added

with accumulator, and counter is again checked for zero.

8085 Programs

Gursharan Singh Tatla Page 3 of 3

If counter becomes zero, then H-L pair is incremented and the result is moved from

accumulator to memory location 3002H.

Output:

Before Execution:

3000H: 02H

3001H: 05H

After Execution:

3002H: 0AH